Cervical Sympathetic Trunk Block

Introduction
Stellate ganglion block is often the term used to describe blockade of the cervical sympathetic trunk. This block is performed for the following indications and purposes for diagnosis or treatment:

The cervical sympathetic trunk, one on each side of the vertebral bodies, carries sympathetic fibers to the head and neck structures. The cervical sympathetic trunk has 3 ganglia: superior, middle and inferior ganglia (Figure 1).

Figure 1. Coronal section of the neck showing the cervical sympathetic trunk and its relation to the prevertebral muscles on each side

The superior cervical ganglion containing C1-4 fibers is usually found opposite the C2 and C3 vertebrae. The middle cervical ganglion containing C5 and C6 fibers is often found opposite the C6 vertebrae. It is the smallest of the 3 cervical ganglia and may be absent. The inferior cervical ganglion containing C7 and C8 fibers is often located between the base of the C7 transverse process and the neck of the 1st rib, on the medial side of the costocervical artery.

Movie 1. Cervical sympathetic ganglia and trunk anatomy

When the inferior cervical ganglion is fused with the T1 ganglion, this cervicothoracic ganglion is called the stellate ganglion. It is often situated posterior to the vertebral artery and the subclavian artery and lateral to the trachea, esophagus and the longus colli muscle. The post-ganglionic fibers of the stellate ganglion provide sympathetic innervation to the upper limbs.

Movie 2. Stellate ganglion anatomy

The prevertebral fascia is a layer of deep cervical fascia that envelops the prevertebral muscles (longus colli and longus capitis muscles) that attach to the cervical vertebral bodies and transverse processes (Figure 2). The cervical sympathetic trunk runs through the prevertebral fascia thus this important structure influences the extent of local anesthetic spread during stellate ganglion block. Success of the cervical sympathetic block relies on proper local anesthetic deposit deep to the prevertebral fascia.

Sonoanatomy
In the transverse view, although the cervical sympathetic trunk is expected to lie between the longus colli muscle and the prevertebral fascia, it may not be easily visualized as a distinct structure until local anesthetic is injected to separate the longus colli muscle from the prevertebral fascia (Figure 3).

Scanning Technique
Position the patient lateral decubitus (with the block side up) or supine.
After skin and transducer preparation, place a linear 38-mm high frequency 10-12 MHz transducer on the skin surface to obtain a best possible transverse view of the neck (Figure 6).
Figure 6. A linear transducer positioned over neck

Optimize machine imaging capability by selecting the appropriate depth of field (usually within 2-4 cm), focus range and gain.

The transducer should be at the level of the C6 transverse process (Figure 7).

the carotid tubercle or anterior tubercle of the C6 transverse process and

trachea (midline).

Helpful internal sonographic landmarks to be recognized at the C6 level are:

sternocleidomastoid muscle;

cricoid cartilage (C6 level);

carotid artery;

anterior tubercle of the C6 transverse process);

infra-hyoid musculature;

longus colli muscle;

trachea;

thyroid gland;

vertebral body; and

esophagus.

First identify the superficial triangular shaped sternoclei-domastoid muscle (SCM).
Then identify the neurovascular landmarks within the carotid sheath which are the carotid artery (CA), internal jugular vein and the vagus nerve. They are deep to the sternocleidomastoid muscle (Figure 8).
Figure 8. Sonoanatomy of neurovascular landmarks within the carotid sheath

CA = carotid arteryIJV = internal jugular vein

Deep to the carotid artery is the longus colli muscle (LC) and the overlying prevertebral fascia (Figure 9). The longus colli muscle lies anterior to the C6 vertebral body. This is the reference muscle for cervical sympathetic block at the C6 level.

Medial to the carotid artery is the thyroid gland (Th), a homogeneously hyperechoic organ. Deep to the thyroid gland is the esophagus (E) which is more readily visible especially on the left side of the neck (Figure 10). The deepest structure is the transverse process (TP, a hyperechoic line with a bony acoustic shadow beneath. Medial to the thyroid gland is the cricoid cartilage and the trachea (T). Both are easily palpable by hand and visible under ultrasound.

Lateral to the carotid artery at the level of C6 is the C6 transverse process with the anterior tubercle (AT) which is more prominent than the posterior tubercle. Both tubercles are seen as bony acoustic shadows. Simply follow the hyperechoic line of the vertebral body laterally to the prominent anterior tubercle of the C6 transverse process.

The hyperechoic cervical sympathetic trunk is expected to lie anterior to the longus colli muscle, posterior to the carotid artery and medial to the anterior tubercle of the C6 transverse process (Figure 11). This is likely where the middle cervical ganglion or trunk is situated. This is not the stellate ganglion which is located more inferiorly (between the C7 transverse process and the first rib).

The prevertebral fascia overlying the longus colli muscle is thin and may appear as a hyperechoic line. However it is not easily visualized under ultrasound most of the time. The prevertebral fascia becomes visualized once it is separated from the longus colli muscle during injection of local anesthetic.

Now identify the optimal site for CST block at the C6 level.

Needle Insertion Approach
Ultrasound guided cervical sympathetic trunk block is considered a BASIC skill level block.
The goal is to block the cervical sympathetic trunk at approximately the C6 level which corresponds to approximately the middle cervical ganglia level. Local anesthetic deposited at C6 will spread caudad to block the stellate ganglion.
To approach the cervical sympathetic trunk at the C6 level, it is advisable to turn the head to the contralateral side of the block. This will bring the cervical sympathetic trunk and the longus colli muscle lateral to the carotid artery, and the vagus nerve.
We recommend an in-plane lateral to medial needle approach (Figure 12).
Figure 12. Transducer and patient position for ultrasound guided cervical sympathetic block

The needle approaching from lateral to medial will first contact the anterior tubercle of the C6 transverse process (Figure 13) and then enter the prevertebral fascia (Figure 14).

The goal is to inject 5 mL of local anesthetic deep to the prevertebral fascia (or called the deep cervical fascia) and above the longus colli muscle (Figure 15). Also aim not to inject local anesthetic into the substance of the longus colli muscle.

When scan caudad to the C6 level, the vertebral artery (VA) and vein (VV) are now in view (Figure 17 13). The stellate ganglion is in the vertebro-scalene triangle at this level. The stellate ganglion is posterior to the vertebral vessels thus difficult to access.

Sonogram at the C7 level showing the longus colli muscle (LC), the vertebral artery and vein (VA & VV) and the vertebral body (VB) as shown in Figures 17 (without Color Doppler) and 18 (with Color Doppler). Note that the C6 transverse process is absent in this view.?

The cervical sympathetic trunk is medial to the C6 transverse process while the C6 nerve root is lateral to the anterior tubercle (AT) of C6 (Figure 19). In this picture, the C6 nerve root is seen exiting the neural foramen at the C6 transverse process.

The cervical sympathetic trunk and the longus colli muscle are usually located deep to the carotid artery when the head is in neutral position (Figure 20). To access the cervical sympathetic trunk for an ultrasound guided procedure, turn the patient's head to the contralateral side so that the sympathetic trunk and the longus colli muscle are displaced more laterally (Figure 21).

Figure 20. Sonogram showing the cervical sympathetic trunk and longus colli muscle deep to the carotid artery when the head is in neutral position

At the vertebro-scalene triangle at C7 or below, the cervicothoracic (stellate) ganglion situated between the C7 transverse process and the first rib is immediately next to the vertebral vessels thus needle access to this region is technically challenging (Figure 22).